(1) Field of the Invention
The present invention relates to an interface for transmitting a digital video signal including an audio signal.
(2) Description of the Related Arts
Digital interfaces for transmitting a digital video signal, such as an HDMI (High Definition Multimedia Interface), a DVI (Digital Visual Interface), and a DisplayPort have been provided from the past.
These digital interfaces are used for transmitting a digital video signal from a video transmitter to a video receiver. The video transmitter is, for example, a digital recorder such as a DVD (Digital Versatile Disc) reproducing device, a STB (Set Top Box), or a personal computer. The video receiver is, for example, a video display device such as a monitor for a television or a personal computer.
In the case of connection through a digital interface such as the HDMI, a CP (Contents Protection, namely, copyright protection) technique such as an HDCP (High-bandwidth digital Contents Protection) is employed, and transmission and reception of a video signal is enabled only when the video transmitter and the video receiver are successfully authenticated.
However, a conventional authentication operation is executed while a HPD terminal is changed its level High to Low to High not only the time of power-on reset of the video receiver, but also every time when the display switch to another input terminal or data related to the characteristics of the video receiver are rewritten. Accordingly, the video transmitter cannot read the data related to the characteristics of the video receiver until the data rewriting is completed, which leads to problems that a video cannot be displayed or an interruption time of a video is long.
Japanese Patent Application Laid-Open No. 2008-252819 describes an example in which data related to the characteristics of a video receiver are rewritten in accordance with a state of the video receiver.
Japanese Patent Application Laid-Open No. 2006-246300 describes an example of a display when authentication fails, but does not describe eliminating or shortening of a video interruption time caused by switching of the input terminal or rewriting of data related to the characteristics of a video receiver